Cervical spinal stenosis is a condition in which the opening for the spinal cord that runs through the vertebrae of the spinal column is not quite wide enough to comfortably accommodate the spinal cord. The result is that when the ligaments thicken or there is some bulging of the cervical discs (a natural product of wear and tear through life) the person who is affected begins to experience pressure on their spinal cord. This causes three types of symptoms:
1. It causes pain in the head, neck and arms; PA1 2. It causes weakness and/or numbness and tingling in the arms; PA1 3. It causes clumsiness in the arms and legs.
As a result of these symptoms, some people find that their mobility and their ability to undertake a normal day's work is severely affected. The obvious solution is to make more room for the spinal cord so that the pressure will not happen. There are two methods of creating more room in the cervical spinal canal. The first is a laminectomy in which the bony structures forming the back of the canal and the associated ligaments are removed. This can lead to the swan neck deformity so that although it is a very safe operation and usually quite effective it can result in swan neck deformity which is a very difficult problem to correct and which itself causes a lot of discomfort in the neck and shoulders. This is due to the lack of the supporting structures at the back of the vertebrae which normally perform some of the work of keeping the neck in the right shape.
The alternative and increasingly popular way of doing the operation is called a laminoplasty. In this operation the back of the spine is exposed but instead of the bony structures being removed, they are altered in shape. When the bone has been weakened it is bent outwards opening the canal and providing more room for the spinal cord. The traditional problem has always been to stabilise the lamina in this new position.
One way of stabilising the lamina is to take a bone graft from the hip in the form of a rectangular plate of bone and wedge it in position to try and hold the lamina in its new, more open shape. This is generally effective but because it is not a firm arrangement can lead to some slippage and recurrent narrowing of the spinal canal. It also involves making a separate wound in the area of the hip and taking a bone graft.
It is an object of the present invention to provide a prosthesis device to dynamically stabilise the lamina after laminoplasty.